/Engine/Source/Runtime/SlateCore/Public/Layout/PaintGeometry.h
Support mutable geometries constructed in window space, and possibly mutated later, as all legacy members are public. In these cases we defer creating of the RenderTransform and LocalSize until rendering time to ensure that all member changes have finished. WARNING: Legacy usage does NOT support render transforms!
void CommitTransformsIfUsingLegacyConstructor() const